The present invention relates to a process for producing an ethylene-α-olefin copolymer.
Ethylene-α-olefin copolymers such as ethylene-α-olefin-conjugated diene copolymers are widely used as materials for automobiles, industrial apparatuses, office appliances, construction materials, etc. As a process for producing the ethylene-α-olefin copolymer, there is known a process which comprises preparing two kinds of ethylene-α-olefin copolymers and melt mixing them for obtaining polymers having desired physical properties depending on the use.
As other process, there is known a process for producing an ethylene-α-olefin copolymer by continuous multistage polymerization using a multistage polymerization reaction apparatus comprising two or more tanks of polymerization reactors connected in series. For example, Patent Document 1 discloses that using a multistage polymerization reaction apparatus comprising two connected polymerization reactors of the same volume, ethylene, propylene and dicyclopentadiene are copolymerized at multistage with a first polymerization reactor and a second polymerization reactor under the same conditions, except for changing the amounts of hydrogen gas and comonomers fed to the first polymerization reactor and the second polymerization reactor. Patent Document 2 shown below discloses that using a multistage polymerization reaction apparatus comprising two connected polymerization reactors of the same volume, ethylene and propylene are copolymerized at multistage with a first polymerization reactor and a second polymerization reactor under the same conditions, except for changing the amounts of hydrogen gas and comonomers and the polymerization temperature between the first polymerization reactor and the second polymerization reactor, and further discloses that the process carried out by the continuous multistage polymerization is economically advantageous.
Patent Document 1: JP-A-55-36251
Patent Document 2: JP-A-2002-505357